The present invention relates generally to pouches and more particularly to an improved method of making pouches.
In recent years, the packaging industry has made extensive use of pouches for packaging various articles. For example, pouches are now extensively used in packaging frozen food products. A pouch of the type herein referred to, consists of two webs of material which are joined along the peripheral edges. The webs will define the pouch side walls while the joined peripheral edges of the side walls define fins.
The normal procedure for making pouches is to join two side walls of material together by a heat sealing process. This procedure requires that at least one of the side walls be of a physical character which can be joined to the other side wall by heat and pressure. If this characteristic is lacking, at least one surface of one of the side walls must be modified to incorporate heat sealing characteristics. This is usually done by laminating a suitable film to the sheet forming one side wall an coating the wall to allow the two side walls to be joined by the heat sealing process.
Thus, webs which do not have heat sealing characteristics are not considered suitable for pouch making since it requires the application of a film or coating to a surface of the material thereby increasing the cost thereof. Another proble encountered in present method of making pouches is that the maximum output of a pouch making machine is severely restricted by the time required for increasing the temperature of the material sufficiently to heat seal the two side walls or webs together.
Even if the additional expense of applying a film or coating or heat sealable material, such as polyethylene treated to incorporate heat sealing properties is justified, a pouch formed in this manner has several undesirable characteristics. For example, coating the entire surface of one of the side walls with a heat sealable material, requires that the contents of the pouch be in contact with the heat sealing film or coating. In addition, the film of heat sealing material, in many instances, will decrease the permeability of the side wall thereby increasing the time required for sterilization of the contents after being placed in the package, which is required for many packaged materials. Also, a large quantity of heat sealing coating or film is applied when in actuality only a small portion thereof is needed.